text:
What happens at a ramp check when I forgot my license and medical?
I wonder what happens if I would get ramp checked and don’t have my license and medical with me. Especially in EASA territory. Anyone ever had this case?

FAA answer, hence the comment.  You'll have problems.  Assuming it is clear that you were flying without those documents, you are in violation of regulations and could face a penalty.  It's ultimately up to the agent, but it is a violation.

Since EASA delegates the implementation of regulations to individual countries it's likely that this depends partly on which country you're in. Different countries may have different penalties. Do you have a specific country in mind, or is it a general question?

@Pondlife Germany and Switzerland. Just asking for a friend. :-)

If you get ramp checked in a country under EASA jurisdiction, they will follow the EASA ramp check SAFA procedures, which include 53 points of inspection, not all of which may be performed during a check. Licenses are part of the inspection. Medical certificates are not mentioned, but I assume they are as well. Discrepancies found can be minor, significant or major. As a former auditor myself, I am going to make an educated guess that not having your license in your possession is the same as not having a license at all and would be a major discrepancy, and might result in the inspector directing the facility not to allow you to depart in your aircraft until you go get your license. It is almost 100% certain that the discrepancy would also be reported to the FAA.
At what stage of the flight the ramp check is performed will also make a difference, of course. Getting ramp checked before you leave and not having your license may result in nothing more than a stern warning and being told to go get it. You will likely not get off as easily if you are ramp checked as you are arriving in your aircraft.
Solution: Follow your checklist and verify your documentation prior to even starting the engine.

"It is almost 100% certain that the discrepancy would also be reported to the FAA" Did you mean to EASA?

Would it help any if the pilot showed electronic copies on their phone/tablet?

No, I meant the FAA. And whether or not the ramp inspector will accept electronic reproductions of the documents is a crapshoot.

@JuanJimenez Isn't there any difference between flying internationally and domestically (in the country of issue of licenses and plane registration)?

@Afe That should be obvious from the fact that I pointed out my answer is for EASA countries. In the US you have to have your license with you or you risk a fine, and maybe even being arrested if the inspector reports it to the police.

@JuanJimenez, Jurisdiction matters… local police have no more authority to arrest you for flying without your pilot certificate than a FSDO inspector would have to pull you over for speeding in your car.

FAA Regulations 61.3(l) and 61.51(i)(1) state that a person must present his or her certificates, authorizations, identification, and other documents required under Part 61 for inspection upon a request by the administrator, NTSB, or any federal, state, or local law enforcement officer. This gives local LEO's the right to arrest you if you refuse to do so. States do not have to reciprocate arrest authority to the FAA for federal regulations to be enforced.


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How can I find out if there's an EASA STC for something that has an FAA STC?
I want to purchase something for my Cessna from a US web shop.
The part has a Supplemental Type Certificate (STC) from the FAA, but I don't find any information about the EASA equivalent.
Is there any database to check this?

I've never heard it called "STA", we always call it "STC"

Thanks for the hint. Corrected it! @selectstriker2

STA, or Supplemental Type Approval, is the term used in Commonwealth countries (UK, Canada, etc.) which is where I'm guessing David is.  Pondlife's edit is correct however, as EASA calls them STCs.

Which STC are you talking about?

Unless I am reading the document incorrectly, EASA and the FAA have a reciprocity agreement since 2011 recognizing each other's findings and approvals. That means an FAA STC approval is good in EASA countries (except the ones that are not EU members) and vice-versa.

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Do I need a waiver to operate a C208B with more than 9 passengers?
Do I need a FAR Part 23 waiver for more than 9 passengers if I'm operating a Cessna 208B Grand Caravan under part 91?

Related: http://aviation.stackexchange.com/questions/8163/why-might-a-cessna-208-need-a-far-part-23-waiver

The discussions for that suggested-as-duplicate question don't really provide an answer to this one.  It talks around the issue, but the two questions are distinct.

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Can I be a pilot now considering the new advancements in color vision lenses and glasses?
I have always wanted to be a pilot but I am red/green color deficient. I passed all other physicals and can easily tell the difference between red and green. I only discovered I had a deficiency after I failed the Ishihara Plates Test (the one with circles of dots with numbers). So I opted for Military Police instead of flight school. However, now color vision contact lenses and glasses are available with a 100% success rate after testing with the Ishihara Plates Test. Does this open any new doors for color deficient applicants in flight schools? I can't find anyone that has answers. Thank you.

We have a retired 747 captain who is color-blind around! Being able to distinguish the color light signals seems to be enough (for civilian career; military is probably out of question).

@JanHudec -- yeah -- for civil aviation, it's simply enough that you be able to work with/around your color vision deficiencies in practice (the medical exams include sets of practical tests, basically, for this).

My brother and several pilots I have known were color blind commercial pilots. In my brothers case, he received a "demonstrated ability" waiver. In other words, he had flown to the point of receiving his PPL and not had any accidents. That served as proof he was a safe pilot. I flunked my eye examination once 40years ago and also got a  "demonstrated ability" waiver - I had 500hrs then. I have never had eye problems since then so I don't know what happened.

According to FAA guide for Aviation Medical Examiners:

F. Color Vision Correcting Lens (e.g. X-Chrom)
Such lenses are unacceptable to the FAA as a means for correcting a pilot's color vision deficiencies.

However, you have the option of taking other tests for color vision. It would be better to talk with your physician or the medical examiner about this.

Just curious, what are the significant differences between these tests for color vision?

The standard for color vision testing is the Ishihara Plates Test. There are other similar test to the Ishihara consisting of more or less Plates. Other test like the Farnsworth Lantern test are available as well but are not as readily accepted depending on the admissions requirements. I have taken both the Farnsworth lantern is basically choosing between red and green which was easy. The Plates Test mixes Dots and several shades making it harder for me personally.

The standard Ishihara Plates Test is almost always administered incorrectly!  The room where you take the test is almost always lit by flourescent lighting, which gives off a blue-ish light that makes a person near the edge of color blindness fail.  Most MDs will let you take the Ishihara test outside in bright sunlight.  Try it!

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Can the ball on a turn coordinator be to the full right/left while the wings are level?
Can it ever happen in a wings level flight that the Turn and Slip indicator ball is to the full right/left? If so then when and what will be the flight path of such an aircraft? Thanks in advance.

Related: Are the functions of ailerons and rudder similar? which shows a wing level skidding turn with ball deflected. Note that in that case, while the wing is level, the turn indicator shows the turn rate to the right.

Yes, when the rudder is highly deflected. The slip indicator gives us information on the yaw axis of the airplane and "level flight" is generally in relation to a neutral pitch and power situation (i.e. not climbing or descending). An aircraft can be yawed with rudder input alone and subsequently cause the slip ball to deflect as appropriate.

When you typed "yaw access", was that a typo for "axis" or "angle" or something else? (Someone else edited it to "axis".)

@TannerSwett my mistake axis is correct

Fun fact: on a twin flying on one engine, the rudder applied to counteract the yawing moment of the live engine redirects the net thrust line toward the dead engine and if you keep wings level you are actually slewing to the right.  You bank into the live engine about 5 deg to create an opposing side slip force, which cancels out the slew to the right.  You end up flying along straight through the air, tilted toward the live engine, with the skid ball offset toward the live engine about a ball width (but aligned with the true vertical axis), in coordinated flight.

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Can multiple aircraft share the same logbook?
If a private pilot owns 3 planes can he use 1 logbook for all 3 or does he need to use 3 logbooks?  Would the answer change if he also owns a helicopter?

Welcome to aviation.SE! Are you asking about pilot logbooks (training, flight time) or aircraft logbooks (maintenance etc.)?

Assuming that you are talking about the pilot logbook and not maintenance logs, he can use one logbook for all three aircraft.  There is a column for aircraft type and registration number, so clearly the intent is to allow a pilot to document time flown in more than one specific aircraft.

If you are asking about airframe/engine/prop records, you should keep separate logs but strictly speaking you may not have to. It would be foolish to combine the records since in the event of a sale of one of the aircraft the records must be passed a long, a complex task if they are all lines in the same log book.
The FAA governs log keeping for aircraft under §91.417   Maintenance records. which tells us what we need to log but does not really tell us how we need to log it in depth. They cover acceptable methods for logging in AC 43-9C - Maintenance Records which interestingly states

Section 91.417(a)(1). Requires a record of maintenance for each
  aircraft (including the airframe) and each engine, propeller, rotor,
  and appliance of an aircraft. This does not require separate or
  individual records for each of these items. It does require the
  information specified in § 91.417(a)(1) through 91.417(a)(2)(vi) to be
  kept for each item as appropriate. As a practical matter, many owners
  and operators find it advantageous to keep separate or individual
  records since it facilitates transfer of the record with the item when
  ownership changes. Section 91.417(a)(1) has no counterpart in § 43.9
  or § 43.11.

this chunk largely applies to keeping separate airframe/prop/engine log books (which most owners do) but technically does not prevent nor explicitly rule out keeping multiple aircraft records in one book.


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How to calculate the flight envelope and maneuvering envelope for the B727-200F?
I'm a student and my assignment is to make a flight envelope and maneuvering envelope of the Boeing 727F-223. But I don't find any of the values to calculate the flight envelope and maneuvering envelope. Can someone tell me how to find these values and how to get started with making the envelopes themselves?

Start with the appropriate sections in FAR part 25. The link is to the current version - you will probably collect bonus points if you dig up the version from the Sixties which was current when Boeing applied for the certification of the 727-223. Once the application is started, the rules remain relevant for that particular type - that is why Boeing redesigned the 737 several times over but kept the old name and the certification regulations that came with it. This is called Grandfather policy.
Calculate the minimum speed curve over load factor, then draw the v-n-diagram and the gust lines for 56 ft/s vertical gusts at sea level and repeat with 44 ft/s gusts at 15,000 ft, decreasing to 20.86 ft/s at 60,000 ft for the current version. Older versions used gusts of 50 or 66 ft/s from sea level to 20,000 ft, decreasing to 25 or 38 ft/s between 20,000 and 50,000 ft - the lower level is for the Sixties, the higher one for the Nineties. Note where the  minimum flight speed line will cross the maximum load factor - this is where your $\text{v}_A$ should go. Next, the limit speed in turbulent weather $\text{v}_B$ is determined by the point where the gust line will reach your maximum load factor. Cruise and dive speed are more tricky, but the limit Mach speeds are even listed in Wikipedia or on Airliners.net.
The negative side will involve some speculation unless you have been given a minimum lift coefficient - use 0.7 times the maximum clean value if you have nothing else. Use the intersection of the minimum lift line with the -1g line to continue horizontally and reduce the envelope between $\text{v}_C$ and $\text{v}_D$ from -1g to 0g, and you are done.


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What is the relation between flap setting and aileron droop on the A350?
The A350 has a aileron droop function, which is linked to the flap setting. In contrast to other aircraft with aileron droop, the  A350s ailerons do not droop when the flaps are fully extended.
I would like to know why the ailerons don´t droop when the flaps are fully deployed, and if possible what the scheduling for the aileron droop looks like in relation to the selected flap setting.

Some of the gliders I fly do the same: They do not droop ailerons in full landing configuration but do in intermediate settings. There the reason is aileron effectiveness at high angle of attack and prevention of a tip stall.
If you droop the ailerons it yields more lift but the angle of attack at which the airfoil stalls is decreased, which might give you a more violent stall. And if you suddenly deflect the aileron down further the flow could separate and cause "the wrong wing to go down". To avoid this airliners are often fitted with vortex generators on the outboard section (e.g. Boeing 737) but that was probably a no-go for the clean A350 wings.
Regarding droop vs. flap setting, the FCOM probably has the answer for that. Couldn't find it online yet. A380 does 5 degrees when flaps reach position 1+F or greater, A320 does 5 degrees when flaps reach 1+F or greater so it might be similar with the A350


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Is there a wordpress plugin for live NOTAMs?
How can I embed live notams to my wordpress webiste?
Is there a plugin to get live NOTAMs updates on my website?

Why do your tags have nothing to do with NOTAMs?

This question is fundamentally about web programming; the fact that the data desired is related to aviation is fairly incidental.  This question would best be posed to a discussion board specializing in WordPress and how to do things like you want there.

I'm also not entirely sure why you'd want to do this, unless it's just for fun/practice, since anyone looking for NOTAMs would want to consult an official source to make sure they're seeing up-to-date valid information instead of someone's wordpress site.

Migrate this to stack overflow and you should get a decent response

@Cloud he won't get help on Stack Overflow - the community at SO is happy to help people who have shown research effort and are struggling with programming issues. And last but not least, questions about plugins, libraries and other external resources are off-topic at SO as stated in https://stackoverflow.com/help/on-topic

@ElmoVanKielmo It's why I gave up there a long time ago.. one of the most useless SE sites

@Cloud not really true. It's just not a replacement for Google search.

People on SO are surprisingly helpful if you say a) here is what I’m trying to do, b) here is what I tried, c) here is the error I’m getting or what is happening instead of what I want to happen. When it is evident from the question that the OP hasn’t even done a Google search then people tend to be less helpful. You have to at least show effort.

As mentioned, this is off-topic and more related to understanding APIs and Wordpress plug-ins.
If you want a place to start:
https://developer.laminardata.aero/documentation/notamdata might give you API access, but you'll have to build it yourself which is beyond the scope of this site.
As @Zach Lipton mentioned in the comments, even the official sites have a disclaimer, but here are a couple official sites you could check out:

https://notams.aim.faa.gov/notamSearch/nsapp.html#/
https://www.notams.faa.gov/dinsQueryWeb/

Somewhat related: Is there a Flights API to get flight information months in advance?

If he is asking about out-the-box plugins, I doubt he is a developer. But good answer, anyway. I suggest this be migrated to SO.


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How do wing tip vortices interact with the airflow on an wing with winglets?
If winglets are added to an aircraft, do the vortices still interact with the airflow and create up wash and down wash. If the vortices do interact with the rest of the flow I am wondering how they do it.
So basically I am asking if wingtip vortices can affect airflow when there are winglets on an aircraft.

Winglets do not change the laws of physics. In particular, they do not change the flow around a wing such that there is no up- or downwash. All they do is to involve a little more air into the creation of lift such that the vortex strength is slightly reduced.
With winglets, wingtip vortices now form at the tip of the winglet instead of at the wingtip. The wake behind the wing still rolls up and creates the usual wake vortices into which the wingtip vortices are absorbed. In order to create the same lift with a slightly less powerful vortex, the distance between both vortices is increased slightly. Actually, in order to support the winglet's weight, the aircraft needs to create slightly more lift with winglets than without, which reduces their benefit.

So, the winglet causes vortices to occur further away from the wing which causes more air to be used for lift creation.

@Crafterguy: Forget the vortices. The winglet allows to involve more air for lift creation. Therefore, more air is accelerated by less.

It depends what you mean by Wingtip Vortices. If you mean the ones from this answer, no amount of winglet will prevent them. These are the consequence of lift creation, and mainly influenced by weight and airspeed.
Strictly speaking, wingtip vortices are only the bit of air that flips around the tip of the wing. A very long winglet would prevent that, but a Cessna would still flop around mightily when it falls into the hole that the A380 wing left behind at approach speed. The wing tip is where lift creation ends, and there is a discontinuity there, winglet or not.

Without winglets the wingtip vortices (or wake turbulence) stabilize at about two thirds of the wingspan. The closer the wake turbulence is to the planes body the more drag is induced.
Winglets virtually extend the wingspan (by a multiple of their own length) so that the wake turbulence stabilizes more distant from the body and thus the winglets reduce the induced drag.

By "stabilize at about two thirds of the wing span", do you mean that the outer third of the wing span does not deflect air downwards? Is the situation you describe in cruise or in approach?

@Koyovis No. The center of the vortex moves from the wing tip towards the planes body aproximatly one third of the wing lenghs while the plane moves away.

You might want to add that the multiple normally starts with 0. As in 0.3.

@PeterKämpf When referencing  the winglet length the multiple is bigger than 1, otherwise a longer wing would be more efficient.

Nonono, check your data. A winglet is approximately as good as a span extension of 30% of the winglet span, given that the aircraft flies mostly at optimum L/D.

@TimothyTruckle: The wing sheds vorticity over the whole span (more precisely, when a lift gradient over span is present), so there is no initial center - this forms only when the wake rolls up behind the wing. The tip vortex is part of that wake system, but not its origin.


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What is the correlation between RNP level and the CDI indication?
I got a question regarding the connection between RNP (required navigational performance) accuracy and cdi sensitivity of the HSI.
According to the instrument flying handbook the standard for RNP on route would be 2Nm from the centerline.
So for me this means, that I will be at least 95% of my flight in that corridor (given, if raim  is available all the time)
So let's say I am off by 1 Nm enroute due to inaccuracy.
According to Rnp that would be still ok, however the question now is, what would my CDI show me?
The gps obviously does not know that it is 1Nm off course (if so why would we have such a thing like rnp of 2Nm) so the CDI should be centered even though I am actually 1Nm off the correct course.
If this is true I theoretically could be e.g. 4 Nm off course even though I got only a 2 dot deflection on my HSI given that a full deflection would represent 5 Nm because it is not WAAS capable (2Nm rnp + 2 Nm for the two dots)
Thanks for you help in advance...

"The gps obviously does not know that it is 1Nm off course". The RNP software knows where is the centerline of your RNP corridor. A GPS receiver without WAAS knows where you are with a practical precision of 15 m times the GDOP value (< 3 in normal conditions, and often < 2). Your position can be even more accurate as it is computed from the INS, the GPS and the available ground aids. The CDI only shows the difference between your known position and the RNP centerline. There is no cumulative error.

So the cdi refereses to the actual centerline which can be provided through the RNP software and shows me the distance to the RNP centerline with a inaccuracy of about 50ft (GPS) and about 10 ft (WAAS). Without RNP the reference to the accurate centerline would not be given and I could be way off because of currupt signal/ not enough satellites?do I got that right? Thanks

The GPS position accuracy is not dependent on RNP. A possible cause of deviation is the inability for the autopilot to follow the intended RNP route. An overall presentation of errors is available at 2.2.1 Lateral navigation (page 100) in ICAO PBN Manual (Doc 9613).

Actually we have two types of systems: either the ADIRUs doesn’t receive the GPS and it is the FMS which will combine the ADIRUs positions, the GPS position and the radio position, or the ADIRUs positions are GPS corrected inside de ADIRUs and the FMS will combine the resultant corrected ADIRUs positions with radio position. In all cases the autopilot is not concerned, this applies to manual flight too. If actual GPS detected precision is less precise than the RNP the FMS will neglect the GPS to calculate your position which becomes a combined radio/ ADIRUs position calculated by the FMS

Please refer to this document for more details, it applies to AIRBUS but also generally to other manufacturers, starting page 21 more precisely :   https://www.theairlinepilots.com/forumarchive/aviation-regulations/rnp-ar.pdf

@Mani, please refer to my previous 2 comments.

The Performance Based Navigation concept allows to optimize the instrument procedure design with the aircraft navigation performance.
This concept is used en route, to reduce aircraft separation, and in terminal area to optimize arrival and departure procedures. The utmost development of Performance Based Navigation for approach, missed approach and departure is known under different names.
FAA initially referred to RNP SAAAR Operations, SAAAR standing for Special Aircraft and Aircrew Authorization Required.
ICAO now refers to RNP Operations with Authorization Required (RNP AR).
The estimation of the aircraft position is performed by the Flight Management System based on different sensors: Inertial (ADIRU), GPS, radio navigation (DME and VOR).
The FMS computes the best aircraft position estimate based on the following hierarchy of navigation modes:

GPS/inertial,
DME/DME/inertial,
VOR/DME/inertial,
Inertial only.

The RNP capability depends on the availability of GPS/IRS integrity.
The GPS integrity mainly depends on the number of received satellites, the FMS will calculate the GPS estimated error as a function of the number of received satellites and which satellites among the most appropriate for the aircraft position.
The ADIRUs are capable to evaluate their own estimated error that they send to the FMS, similarly the FMS itself is able to calculate the ADIRUs  drift error based on previous ILS landing(if any)  as he compares the ADIRU position to the real aircraft position while on the ILS, This error is reduced to a mean average drift per hour of flight.
The FMS therefore is able to calculate an Estimated Position Error (EPE), thus allowing the CDU to display both the Required Precision, and the Estimated precision
With respect to the HSI, it displays a route as well the approach calculated by the FMS, within the estimated precision which normally is better than the required precision, the pilot is supposed to be on the route and not one dot  or 2 dots apart. When the CDI is centered you are within the Estimated Error;  However indeed if the CDI is not centered the error is augmented as you say in the question, but you should not add the RNP but the Estimated NP that shows on the CDU, because the FMS calculations are normally correct.
Of course if your equipments are faulty and mysteriously the multiple faults are not detected you may be neither within the RNP nor within the ENP.
Please refer to the following website for more details:
https://www.theairlinepilots.com/forumarchive/aviation-regulations/rnp-ar.pdf

The CDI shows how far you are from where the navigator thinks you should be.
RNP refers to how wrong the navigator itself is allowed to be. ANP is how wrong it thinks it may be at any given moment, which is a weird concept. As long as ANP is better (lower) than RNP, you're legal.
CDI deviation and ANP are additive, as you might expect, but note that they may have different signs. For instance, if the CDI shows you're a mile east and the ANP is one mile, you might be in the correct position (if the nav error is a mile west) or two miles east (if the nav error is also a mile east). You just don't know. Obviously, the lower (better) the ANP, the more certain you can be about your location.
Thosr two cases will look the same to the pilot because the navigator has no clue in which direction it is wrong; if it did, it would simply adjust its calculated position to have no error at all.


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Can a US PPL holder log ASES time in Canada while flying with a local FI?
I am an FAA PPL, and I'll be visiting Canada. I'd like to log some seaplane time while I'm there. Can I log ASES dual-received time with any Canadian instructor, or do they need to hold an FAA CFI certificate?

In general, you can log time in foreign aircraft. For training time specifically, the foreign instructor must hold an ICAO-compliant license, per 14 CFR 61.41.
So it should be no problem in your situation.


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How is a glider recovered and returned to an airport after landing in a field?
If a glider has a safe normal landing in a cow pasture or other farm field and has no damage, how is it typically recovered to be returned to an airport for a future flight?  Are the wings designed for quick/easy removal and the wings and fuselage are just hand-carried to a long trailer waiting on a nearby road?  That's kind of how it's done (I believe) with balloon landings, but not sure what the process is for gliders.

FYI Usually glider pilots plan their flights so that they are always in range of an airport. Field landings are pretty rare.

@TylerDurden For XC flights field landings are very common. Yesterday eleven gliders took off at my airfield and seven of them had field landings. We don't plan to be in airport range but in "field range". In regions like the Alps there are even "field landing catalogs" which people use to plan their flights.

@Gypaets Maybe in rural Switzerland that works, but landing outfield in New England 70% of the time would be a life-limiting course of action.

@TylerDurden: there are of course places where outlandings are complicated, and maybe New England is one of those. But in the vast majority of places where gliders are flown, outlandings are possible, and common. Definitely not rare. I have personally outlanded many times, and have done even more retrieves of other pilots; both in club flying, and in competitions. Of my 30+ outlandings, as far as I can remember only one was at an airport.

All gliders can be disassembled to take off wings and elevator.
For each glider type there is a car trailer into which the glider fits after disassembling.

Here you see the “reverse” process (assembly):

Even Matchbox gliders can be recovered.

In our club, before every cross-country flight, a "pick-up" party is appointed and "paid" in the local bar  if the service is needed

Trailering is the most common, however at some of our club's select off airport spots, we had landowner's permission, and I would land the Pawnee and the crew with the trailer would show up for a launch.  It saves the time of disassembly and reassembly.  But for most glider pilots the norm for an off-airport landing is to trailer the craft to the airport.


text:
Are there any airports with multi-level taxiways?
There are many airports where roads (and pedestrian walkways) are routed underneath taxiways, runways, etc. But are there any airports where airplane taxiways go under/over each other?
I can't imagine there would be (for many logistical and sanity reasons), but in this world of unusual design and construction paradigms, I've learned to not say that something has never been done.  This could either be airports that are currently in use, or ones where they were used at one time, but are no longer active.

A logistical difficulty in putting anything above a taxiway, nevermind another taxiway, is leaving clearance for tall tailfins and for wings much wider than the landing gear.

London Gatwick has a pedestrian footbridge over a taxiway. There are a LOT of steps (actually escalators) to get up to it.

If you allow taxiway to also mean a surface where an airplane rolls but not under its own power, then there's the lower decks of an aircraft carrier, and Schätz's carousel hangars.  Note that even Schätz prefers scissors lifts to multilevel tarmac.
Multilevel tarmac would means ramps between levels, which is commonplace for surface vehicles but rare for airplanes, both in airframe design and in pilot training.

The reason is the grading (inclination). There should be enough clearance, and so you need either a very long ramp (which which remove many alternate intersecting, so not really solving problems, if it is at border, just make a parallel taxiway) or a step ramp, which will have many problems: you need a different handling of plane (breaks, power) which pilots are not used, and airplane manufacturers have not certified.
In Switzerland we have few taxiways which go under a road, together a level intersection, but used just for army (ant to go to hangars under mountains). I assume that aircrafts are towed (and military aircrafts are small). In case of war the road is closed and they have normal taxiway.  And so you can see aircraft to have two level of taxiways.


text:
Can someone identify this biplane?
My grandfather in the back seat apparently.

It is a British Airco DH9A light bomber.
Some more info: According to an RAF database, this particular aircraft with registration E848 served in RAF No. 27 and No. 30 squadrons. Both of these squadrons flew sorties over India and the Middle East after World War I (hence the additional radiator fitted under the fuselage to operate in warmer climates, well spotted by Peter Kämpf), but I can't find anything more specific about E848 that would place it in either squadron in particular at any specific point in history.

Light is the word for it.

Minor detail: It has the additional radiator fitted under the fuselage to operate in the Middle East in the 1920s (in a particularly shameful episode of British warfare).

@PeterKämpf Wow, well spotted! You've motivated me to try to find out a bit more about the history of this particular aircraft ...

@PeterKämpf: Would that be the one where the RAF bombed the Kurds with mustard gas?


text:
How common are go-arounds at Penghu Airport?
A friend mentioned being a passenger during a commercial aircraft landing at Taiwan's Penghu Airport (MZG, RCQC) where they had almost touched down but had to abort and keep going due to sudden wind event causing "scary motion". They circled back around and landed minutes later uneventfully.
I'm sure there are standard aviation terms for these but I don't know them.
I mentioned that these happen somewhat regularly especially at certain airports and that one of the first thing student pilots learn is how to do touch-and-go's.
Now I'm curious if there are rough numbers for how often this happens per year and if airports like Penghu's see these more frequently? Something like one out of every 100 days an aircraft has to come around and try again at that airport, or one landing out of 10,000 or similar type of summary statistic.

Help with tags is welcome, as are any edits to improve on my lack of the proper aviation vocabulary.

Related: How common are cancelled landing attempts?

@Bianfable Thanks! There's a lot there about Heathrow and that is already useful to me. But I'm hoping for something more specific to MZG if possible.

YouTube: Magong Airport in Penghu recognized as challenging place to land

I can't find anything particular about Penghu, but the FAA has published some numbers in this PDF on page 12: "average go-arounds across all Core 30 airports were 0.3 percent".

0.3% doesn't seem like much until you realize that 0.3% of 11 million flights is 33,000 go-arounds (at the 30 busiest airports only) which is 90 per day, or 3 per day per airport, on average. So, about 1 every 8 hours at the 30 largest US airports.

Hey, @Bianfable, between you & me, I think we've got an answer (well, sorta...). You did the hard digging, I just did some math - feel free to write it up and you'll get my vote.

@FreeMan Yes, we have the general numbers, but I have nothing specific on Penghu. Without that this is just a duplicate of How often do commercial flights go-around?, ironically your question from 5 years ago. The answer there also says "1–3 per 1000 approaches", which agrees with the FAA number I found.

Ha! thought that sounded familiar... ;)

@Bianfable The general numbers are already helpful to me and I appreciate all of the effort. Penghu might be especially challenging for statistics because it seems to be domestic-only flights, is almost completely dependent on tourist traffic, sits in the center of an "interesting region" and where the culture isn't particularly enthusiastic about explicitly quantifying things associated with bad luck or danger. Thus this may not turn out to be answerable quantitatively due to lack of authoritative sources.


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Did this aircraft illegally exceed 250kts below 10,000ft?
As far as my knowledge goes: There is a 250 kt speed limit under the altitude of 10.000 feet. This screenshot seem to show an aircraft below 10.000 feet and traveling at 285 kts at the time i captured the screenshot.
I don't think this aircraft posed any threats to other aviation traffic as there is no other traffic in the airspace. I was just curious.
EDIT:
Shortly after: I see this aircraft taking off from the same airport. Doing the same thing as the first plane.

The speed in flightradar24 is IAS?

Well it is a ADS-B feed from the aircrafts transponder. So im not sure if it is airspeed or ground speed.

It can be either: http://adsb.tc.faa.gov/WG3_Meetings/Meeting30/1090-WP30-21-Appendix_A%20Mods.pdf

First of all, this aircraft was flying in Europe, not in FAA land. In Europe there is no general limitation to 250 knots below 10000 ft. There is no EASA airspace restrictions, every country has their own set of rules. There are airspaces that have speed restrictions below 10000 ft, others don't and sometimes aircraft are allowed to go faster than 250 knots with ATC permission.
Secondly, the 250 knots is an indicated airspeed limitation. At 10000 ft, 250 KIAS (Knots Indicated Air Speed) will be approximately 289 KTAS (Knots True Air Speed). And then there is the additional effect of wind. With a strong tailwind you can exceed 350 knots ground speed while still flying below 250 KIAS.
Thirdly, the data in the image you linked is provided by ADS-B. ADS-B can transmit either ground speed or air speed. Under the European ADS-B mandate, aircraft must transmit ground speed, not air speed. But since this mandate will not affect this particular aircraft until December 7, 2017 it might very well be transmitting True Air Speed.
Note that ADS-B data is not purely derived from GPS. The Mode S transponder which provides the ADS-B out functionality on this aircraft is attached to various data channels and is getting Indicated Airspeed, barometric vertical rate. In fact ADS-B vertical rate is preferably from a barometric source.


text:
What is this odd aircraft?

What is this aircraft? It was parked at transient parking at the Southern California Logistics Airport.  It is a pusher prop driven plane with a conventional tail.  High aspect ratio un-swept wings.  Odd shaped fuselage.  Any ideas?

When did you see it?

This was yesterday 4/12.

The dark lines well below the mid-line combine with the 2 small windows to create a very bizarre optical effect makes it look like it's tilted to the plane's left. It took a fair bit of looking to realize that I'm only seeing 2 of 4 cockpit windows and that those stripes are not mid-line stripes.

@mins The prop is behind the tail. It is not ducted.

When you took the picture you should have hollered at those people by the wing to get info.

This bullet-shaped fuselage (resembling a Mini-Imp) is very large, maybe 2m in diameter. I don't see any obvious reason for a large body, except for large fuel tanks. The round section is more frequently seen in gliders, but at a smaller size. This seems also too large for a drone. On the other hand gears are light, could fuel be gaseous, which would also favor this round section? The large vertical stabilizer seems to indicate a slow aircraft.

It looks like something Burt Rutan built when he was twelve years old.

@mins I'd say the large vertical stabilizer has more to do with the pusher configuration than speed.  I expect the cg is near the quarter cord of the wing which is fairly far aft due to the pusher engine/prop,  With that short moment arm to the tail, you need a bigger tail surface.  It's the same reason the much faster B747SP had an extra tall vertical stabilizer.

What part of the facility was this picture taken in?  It might help us narrow the purpose down, e.g. is it an experimental government plane?  a cargo test plane?

also, were there any visible markings or logos besides the black stripe down the side?  halfway down the middle there appears to be a logo, maybe lockheed martin?

@FreeMan further adding to that effect is what appears to be a nose wheel canted at a similar angle.

I'd like to name this, the Bean About, or how about the Aerosule or the Caplane, how about the Thunder Dodo?

Could it just be a film prop and not a "real" airplane?  I know that sometimes happens around Southern CA.

Any idea what task the forklift had in the operation? It comes across as a bit odd for the situation.

Single or twin?

I'd guess it's an experimental since you don't see many production planes with no windows for the passengers and forklifts out on the ramp with them. Reminds me of a Piaggio but no idea what it is.

There was a prototype similar to this in the 80's, which was not a Piaggio, but was similar, with a low ground clearance.  In a prototype or a survey aircraft the need for pax windows is not high.  I can remember reading the blurb on the article I recall, because it was similar to the Avanti, but did not have the fake canard that the Avanti has for stability.

@mins, let's consider it is not a "ground mockup", from what we can see:

fuselage shape
the propulsion arrangement
the high aspect ratio wing

Could be a flying prototype to test Boundary Layer Ingestion. So first they keep an open propeller to test the (unusual) configuration, and then once vrified it is flyable, they will install the BLI equipment.
I would not know why that airfield tough, I would expect something like that from NASA...

@mins I like the gaseous fuel guess. Hydrogen fueled perhaps?

FYI this is now a minor news story; CNN has linked OP's tweet about this question in the article above.

It appears to be a Celera 500L, owned by Otto Aviation Group.

This article has more information: "Unmasking The Bullet-Shaped Mystery Aircraft After It Reemerges At Victorville"

The registration also provides us with a designation for this mystery
  plane—the Celera 500L. It is the only aircraft registered by the
  company with the FAA. The War Zone contacted the Otto Aviation Group
  by phone and they said they could not comment on the aircraft in any
  way.
This new high resolution image shows the rear of the airframe, which
  is the perfect companion photo to the lower resolution, front aspect
  image that we posted last April. We can now clearly see the five
  bladed, variable pitch, "pusher" propeller that will provide thrust.
  The airframe also features what appears to be all-moving vertical and
  horizontal stabilizers, and long, slender wings that are likely
  optimized for laminar flow.
The Bell X-1 like teardrop fuselage design, which includes a cockpit
  windscreen seamlessly blended into the fuselage, gives the aircraft a
  large internal volume and high aerodynamic efficiency. It's safe to
  say that efficiency is what this aircraft is primarily about. Even the
  prop size looks small in relation to the overall aircraft, which would
  point to the possibility that it makes very good use out of the thrust
  it has on hand.

Interesting that the article claims that they broke the story on it. Their "break" came from somebody Tweeting the pic & link in the OP!

Yeah, that was my tweet :)

$\sf \color {SteelBlue} {\text {Known facts}}$

Seen at Southern California Logistics Airport (Victoville, KVCV)
Parked at transient parking
On April 12th, 2017

$\sf \color {SteelBlue} {\text {Aircraft apparent characteristics}}$

Pusher
Propeller behind tail, not ducted
High aspect ratio un-swept wings
Light wheels/gears
Low ground clearance
Maybe 2m diameter fuselage

$\sf \color {SteelBlue} {\text {Unknown so far}}$

Is it a mock-up? A film prop?
What part of the facility was the plane parked on? It might help us narrow the purpose down, e.g. is it an experimental government plane? a cargo test plane?
Were there any visible markings or logos (halfway down the middle there appears to be a logo, maybe Lockheed-Martin)
Single or twin?
mission type?

$\sf \color {SteelBlue} {\text {Intriguing}}$

Bullet symmetrical shape
Why no passengers windows?
Cockpit windows not bulging out of the nose/fuselage shape
Why a so large fuselage (and no windows)? Cargo?
What task the forklift has in the operation? Cargo loading?

$\sf \color {SteelBlue} {\text {Unlikely}}$

Aircraft in production (nobody in the community knows of an exact production aircraft)
unmanned (can be optionally piloted though)

$\sf \color {SteelBlue} {\text {Possibilities}}$

It's a test aircraft
It's not the final shape
The large vertical stabilizer/rudder is linked to the pusher configuration
Experimental since you don't see many production planes with no windows for the passengers and forklifts out on the ramp with them.
From what we can see: - fuselage shape - the propulsion arrangement - the high aspect ratio wing, could be a flying prototype to test Boundary Layer Ingestion. First they keep an open propeller to test the (unusual) configuration, and then once verified it is flyable, they will install the BLI equipment. I would expect something like that from NASA
it's likely a cargo aircraft for short range and small medium sized parcels, goods, etc. considering the location, it can be a test aircraft of one of the high tech companies (google, amazon, etc)

$\sf \color {SteelBlue} {\text {Similarities}}$

Rutan's design (when he was 12)
Piaggio P180 Avanti
Bell X1
Vanilla Aircraft VA001 (UAS)
There was a prototype similar to this in the 80's, which was not a Piaggio, but was similar, with a low ground clearance. It looked like the Avanti, but did not have the fake canard that the Avanti has for stability.
Airbus VoltAir
Airbus E-Fan (fuselage)
Cobalt Co50 Valkyrie (Single pusher engine configuration, first flight January 2015. Too small and dual vertical stabilizers.)

I also rearched in drones images, without success, because to me looks like it's impossible for the pilot to properly see the runway in VRF landing

The Avanti foreplane is not destabilising, as it has the necessary angle of incidence to maintain stability. This also ensures that it stalls before the main wing does, causing the nose to drop and a major stall to be averted. Nor is it fake - its purpose is to offload the tail, allowing both tail and main wing to be smaller.


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What is the name of this vintage helicopter trainer?
I am curious about the tiny training helicopters that can be seen from the second 0:10 in this vintage video about the Cuatro Vientos helicopter school, near Madrid.

Were they "real" helicopters, capable of flying?
Were they a mass-produced model or an artisan solution? Who made them?

Similar trainers are still made

It is a Flettner Bo102 Helitrainer. There were 18 of these produced which were used by six countries.

Source: Airus Helicopter History
Here are some more pictures
It is also known as the Bölkow Bo 102 (Wikipedia).
From Aviastar.org:

Rolled out in 1959, this Helicopter Trainer was powered by a 40hp ILO piston engine and had a twenty-one foot counterbalanced fibreglass rotor blade. In all eighteen of these HeliTrainers were built operating throughout Europe, training military helicopter pilots. Although unable to fly, they were ideal for the teaching of hovering techniques and were replaced by dual trainer helicopters.
The Bo-102 Helitrainer, powered by a 40hp Hirth engine driving a simple one-bladed rotor with a counterweight, was developed in land and water based versions, both of which were semi-captive. This feature allowed the helicopter to rise to a height of 0.6m, turn around a vertical axis and dip at up to 6� but prevented it from flying outside these limits.


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Is it normal procedure to lower flaps at high altitudes?
I was flying on a Boeing 747-800 today and the pilot opened up flaps at high altitude. This caused sharp descend for about 5 seconds ( Causing slight panic onboard ) , the pilot leveled the flaps again after about a minute and the aircraft became much smoother. Is it normal to use flaps like these or this might be an error?

Do you maybe have a picture, a more detailed description of what you saw or a flight number? As flaps increase the lift-to-drag ratio, I'd suspect the aircraft would've climbed. Spoiler or speed brake deployment seems more likely.

Flaps are the the parts that come out and down from the trailing edge. Spoilers are the things that come up from the middle of the wing. Which ones did you see?

@Bram, flaps (and spoilers) are generally used to increase angle of descent at a given speed, as does reducing power and pitching down.  You do get more lift from flaps, but at the expense of much more drag.  The 747 may have been getting out of someone's way.  Agree it may have been spoiler, or perhaps both (as a speed brake).  May have been nice if the pilot intercomed what was going on.

What you saw and felt was the normal operation of the Speed Brakes.
Speed Brakes can also be called Spoilers. They are panels on the top of the wing which open up to create  drag and reduce lift. Some of the panels are also used for roll control.
They are often used in flight when ATC requires a steep descent or an immeadiate reduction in airspeed. They are also used in an Emergency Descent in case of cabin pressure loss. During landings they automatically deploy to increase wheel brake effectiveness.

I think i misunderstood the part and it may infact be speed brakes. Thank you for the picture and explanation


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Can the maximum thrust of a turbofan engine be estimated by its intake diameter?
I have no clue in aeronautics. How to estimate maximum thrust (at any rated condition, such as altitude, speed, rotation velocity- any given condition) by intake diameter?

No.
You need to know one more parameter: How much fuel will be consumed per unit of time. In the end, thrust is created from heating some of the air entering that engine, and only if you know what proportion of air will be used for combustion can you make valid estimates of the thrust than can be generated.
What you can calculate from the intake diameter is how much air flows through the engine per time. The flow speed at the engine face is about Mach 0.5, almost regardless of aircraft speed, so the mass flow is strongly correlated with engine size. The plot below is from NASA TM-X 73,199 which lists statistical data on weight and dimensions of turbofan engines. Unfortunately, it is now more than 40 years old, but the laws of physics have not changed since then.

Correlation of intake diameter with the square root of mass flow from NASA TM-X 73,199. Wa is the air mass flow and h/t is the hub-to-tip ratio of the fan. $\left(1-\left(\frac{h}{t}\right)^2\right)$ is proportional to the effective fan area.
Now this uses fan diameter, not intake diameter, as the basis for the correlation, but those two dimensions are closely correlated, too. For a first order estimate, you can assume $D_F\cdot\sqrt{1-\left(\frac{h}{t}\right)^2}$ to be equal to the intake diameter.
The next step is to get a grasp on the ratio between core flow (which is available for combustion) and secondary flow (which only goes through the fan and exits the engine without being heated by combustion). This ratio is called bypass ratio (BPR) and has grown over time from 0.25 for the RR Conway, the first operational turbofan from the late Fifties, to 11 for the newest version of the CFM LEAP-1A engine on the A320 NEO. Core flow is Wa/BPR.
The fuel-to-air ratio of turbofans is roughly constant at 0.03. Given the bypass ratio you can now calculate the fuel flow and then continue to the thrust by using the specific thrust (thrust per unit of fuel) from sources like Wikibooks or statistical analysis. Note that specific thrust changes with aircraft speed, altitude and bypass ratio!

Thrust specific fuel consumption over Mach for different engine types. Page 29 from Jack Mattingly: Elements of Gas Turbine Propulsion. McGraw-Hill, 1996

Great, thank you, very interesting and detailed.

What part of the thrust is generated by the bypassed air? Obviously it depends, but is there a working point when most of the thrust comes from the bypass?

@GregoryKornblum: Generally, higher bypass ratios (obviously) and higher thrust settings make the bypass air create a higher fraction of total thrust. At low settings, most power is needed to keep the core spinning. See here for more.

I can't find a way to privately message you. Do you mind having a conversation over email?

@GregoryKornblum: Why not post another question here?

I don't feel confident enough with the next question :) not for a public forum.

@GregoryKornblum: I think you should be able to guess my gmail address. Give it a try.

Ok, i have tried five most obvious options, hope it's one of them :) my gmail is lapserdak, please check


text:
What is the standard power supply and voltage supply on modern airliners?
I'm looking at reducing the weight footprint of some of the computer systems on a commercial liner. A big consumer of weight seems to be in power supplies and conversion. Being a computer guy, I don't know anything about avionics or electricity on commercial liners.
Is there a standard power supply or voltage supply for modern air liners?

There are very specialized standards for airborne power supplies, and electronics in general, with specs such as DO-160, DO-178, 400 Hz/AC wild systems, HIRF and lightning resistance, FAA TSO, etc. You're going to have to be a specialist power supply designer to make something that will be allowed to fly. There's no way to take something intended for consumer or commercial use and install it in an aircraft.

Typically 115 VAC, 400 Hz for most large aircraft, which can be rectified and stepped down for DC powered subsystems.  Smaller GA airplanes typically use 12, 14 or 28 VDC for their electrical systems.

Since we are dealing with a computer system, and consistency is important, Is there any standard on how dirty the current can be?  Example: They say 28 VDC, but that can drop at any time to 12 VDC for about 30 seconds.

@RustyWeber usually the voltage won't drop, the frequency will. "Dirty" power is power that has harmonics or noise in the lines, not voltage drops. A voltage drop like that would be a serious problem, frequency is usually OK with +/- some percentage, in grid systems (like in your home) 58-62hz would be OK, outside of that is cause for alarm at the power plant.

@RonBeyer Not on anything designed A380 and onwards (A350, 787, C-Series). All new designs use variable frequency AC. AC frequency will swing between 380 to 800 Hz depending on engine speed.

We also see 115 VAC 60 Hz. The 787 has 230(235) VAC variable frequency from the engine driven generators

They’re not generating electricity at 115 VAC 60 Hz, that’s being created from 400 Hz AC current through a solid state rectifier.  Low frequency AC generators are too heavy for use in aircraft.

True, the power generation isn't done at 115 VAC / 60Hz, but there are those busses as part of the Power Distribution Systems on a wide variety of aircraft

They're actually 3 phase AC systems, so there's a number of 3-phase and 200 V loads in a 115 VAC system, like galley ovens and pitot heaters.

As far is power sourcing goes, transport jets tend to be AC dominant, with most power generated by a/c generators on the engines, and because some of the equipment is frequency sensitive, the main AC generators use a constant speed drive to produce fixed frequency 115vac/400hz as the primary power source.  A minority of the power will be DC, produced by Transformer Rectifier Units that produce 28 volts DC from the AC bus.  Most large jet engines are started by air turbine starters powered by bleed air, so on jets the batteries are only used for backup power for basic DC services and to start the Auxiliary Power Unit, which normally supplies bleed for engine starting.  If the APU is inop, a jet will need a ground bleed source, or a bleed source from another aircraft using a buddy connection.
Turboprops (and perhaps some smaller jets) tend to be the other way around with a 28 VDC dominant power system, with DC generation from the engines using double-duty starter/generators, and the battery is the starting power source.  The engine may also have a variable frequency 115 VAC generator for running non-frequency sensitive components like anti-icing heaters where the higher voltage AC is more efficient.  For frequency sensitive avionics, fixed frequency 115/400 hz power comes from static inverters that convert some of the DC power.
Because of the dependence on electric power for main engine starting, turboprops have to have much larger batteries than similar sized jets.  And of course watt for watt the DC airplane will have a little bit heavier wiring.


text:
Does weight affect the fuel burn calculations in a light GA airplane?
When calculating fuel burn in say a Piper Archer, I usually just use the conservative estimate of 10GPH, but, does the weight of the aircraft affect my fuel burn?
Assuming I have full fuel and am taking off a max takeoff weight, will I still burn the same amount of fuel in 4 hours as I would if I took off with only myself in the plane and full fuel?

When cruising around, are you setting the throttle to a particular power level, or are you trying to maintain a specific airspeed?

I'm setting a power level and accepting the airspeed.

The engine doesn't care how heavy the airplane is (or how well it is flying), but you might.
As long as you are cruising around at a particular altitude and power setting, then the engine is going to consume fuel at the same rate.  A heavier airplane will require increased lift, which will induce greater drag, and will have a lower forward airspeed as a result of that same power (assuming it is not so heavy that it prevents you from maintaining altitude).
If on the other hand you have a particular airspeed you want to maintain, then the power needed for that speed will depend on weight.  Lower weight, less power necessary, less fuel flow required to supply the power.

More weight means the plane will need more lift, and more lift implies more drag. For example, and for a constant airspeed, an increment of 10% in weight will mean 10% more lift, achieved by increasing the AoA, and that will mean 10% more drag too. The power required will be 10% higher also, implying 10% more fuel consumption...
For heavier loads, the relation would not be so (approximately) linear, because the airspeed will be probably lower, the AoA higher, and the induced drag far higher. Thus, the power required (and the fuel consumption) will rise disproportionately.

In short, yes.  However the limited flight envelope and useful loads for these kinds of airplanes combined with limited increase of induced drag will only decrease speed a few knots or so between the airplanes empty weight and maximum takeoff weights.  This only translates to a couple of extra gallons in fuel savings.
To compensate for this, the OEM approved performance charts and flight planning literature in the AFM are usually done at the maximum takeoff weight of the airplane for conservative purposes; the airplane may perform slightly better in optimum conditions but manufacturers err on the safe side for the average private pilot.

Short answer is: you would burn more fuel.
1 You need more energy to counteract gravity during the climb.
2 At a given speed, a higher mass requires more lift, and more lift implies more drag, more drag requires a higher power setting to achieve the same speed, and a higher power setting means a higher fuel flow.
Your POH (part 5) might explain how to calculate the new required fuel.


text:
When/how to set the inbound or outbound course when intercepting a VOR for a DME hold?
I have question for holding pattern.
As I know, when I do DME holding I have to intercept VOR radial and decide entry.
However, when I do this I am so confused and do not know how I can select inbound or outbound course.
For example, One instruction is [Hold SE 325R ABC VOR 13 DME Left]
In this case, my instructor says "try to intercept outbound course 145 and make a holding."
However, another instruction is [Hold NW 330R ABC VOR 12 DME]
In this case, my instructor says "set inbound course 150 and make a holding."
In both cases, the position of aircraft was NW from the ABC VOR, and my heading was 150 and distance was almost 18 DME from the ABC VOR.
This is what I confuse that first instruction was setting outbound, but second instruction was setting inbound course for intercepting the radial.
Could you let me know how I can figure out when I set inbound course or outbound course for intercept one for DME holding?
*I use G1000 which has HSI.
Thank you for your work and time!


text:
When the aircraft tires are "worn to limits", should it be recorded as a pireps or mareps?
How should be correct recorded when the aircraft tires are "worn to limits" - as a pireps or mareps (the data is reflected in the reliability report)

Welcome to Av.SE.  I'm unfamiliar with both of those terms in the context of reporting aircraft defects, and I suspect that will be true of most people here on this forum. Without more context such as what operation or organization you're referencing, this question is likely to be closed as 'unclear what you're asking.'

A "PIREP" (pilot-report) is an in-flight report of weather or other things that other aircraft should be aware of that ATC may not know.
I'm not sure what MAREP you are referring to, the only one I can find is a "marine report" which wouldn't apply here, so I assume you mean "maintenance report".
If you are talking about a commercial aircraft, this would be noted in the aircraft log and the pilot would call maintenance to have the tire changed. This may go in the "maintenance report" you are talking about.
If you are talking about private aircraft, this would be called a "Squawk" and either the pilot would remove the tire and have it changed, or the aircraft would be brought to the closest maintenance facility for service.


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Why use a single engine plane instead of a multi engine one for a long range flight record?
Tupolev ANT-25 was designed specifically for setting flight range records. In 1937 two flights from Moscow, Soviet Union to USA via the North Pole happened - one covered 9130 kilometers and finished in Vancouver, Washington and another covered 11500 kilometers and finished near San Jacinto, California.
ANT-25 had a single V-12 piston engine. This sounds kinda not very redundant - should a single engine fail while the plane was crossing Arctic there was good chance the flight would end there and maybe the crew would not be rescued because simply reaching there would be problematic.
Why was a single engine airplane selected for this specific task where reliability was very important?

In a long range flight record, the most important thing is not the reliability, is the fuel consumption! And the less engines you have, the lower the weight and the consumption.

@GianniAlessandro There's no record if the plane disappears in Arctic.

The Soviet Union had a pragmatic approach to these things, if the plane disappeared then there was no record attempt, if they did then they'd let the world know.

Fuel efficiency. One engine can run more efficiently than two, even if the two have the same power output combined than the one. Friction losses, inertia losses, etc...
The same thing can be seen in commercial airliners today. Now that gas turbines have reached a very reliable state, and the regulations for overwater flight recognize this, we are seeing large two engine widebodies (777) replacing four engine widebodies (A340), partially due to lower maintenance costs (cheaper to rebuild two large engines than four smaller ones) but mainly for reasons of fuel consumption.
The Voyager that made the round the world unrefueled flight had two engines, but only used both for takeoff and initial climb. After that, the one was shut down for the duration of the flight, for reasons of fuel consumption.
Obviously, two engines are more reliable than one, and yes, a single engine long range flight is risky.

Two engines have twice the chance of a failure, amd are therefore less reliable than one engine. It's the effect of a failure that is less in a twin.

True, but the effect of the loss is what matters. While single engine operation on a dual engine aircraft can be difficult, no engine operation on a single engine aircraft is going to end very quickly. Best to consider the reliability of an aircraft in total, not just one component.

Reliability as in chance of a failure?

Reliability as in the flight coming to an unexpected end.

As said in the comments, in a distance record aircraft you want to keep the drag and mass of your aircraft as low as possible. The previous and next record were flown in single engines too and risk assessment was a bit different back then.
Using a single engine for such long distances wasn't the only ANT-25 characteristic you wouldn't see in a normal airplane: the engine was underpowered (only Russian production engine available?) and for record flights the whole aircraft was even lack-stripped in order to weight less.
For emergency landings in the arctic they had skis, tents and other gear stored in the wings.
In the case of having to land on water they would jettison part of the fuel and inflate some kind of balloons which were inside the wings. That way the wings could be used as floating bodies and prevent water from entering. After water-ditching with retracted landing gear the aircraft could apparently stay afloat for a long time.
If you're interested in further details this biography of Pavel Sukhoi describes the project thoroughly in one of the chapters.


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Can a CFI whose instrument rating isn't valid legally offer instrument instruction?
Can a flight instructor whose instrument rating isn't valid legally offer instrument instruction?

Not valid as in revoked/limited or not valid as in, not current for IFR operations (does not meet FAR61.3) depending on interpretation the answers may vary quite a bit.

Welcome to aviation.SE! For questions about regulations, please always tell us which country you're asking about. The [tour] may be helpful if you're new to StackExchange.

Ground or flight? In IMC or in VMC?

if a CFII is not IFR current, they can still offer training on a simulator, or offer training in IFR simulated conditions (e.g. hood time) while the CFII is flying in VFR conditions

In order to provide instrument instruction, the instructor must hold a CFI Instrument, or CFII. They must also be Instrument current in order to file/fly under IFR.

A few issues here
Instrument currency - Per 61.56(c), you must be Instrument current to serve as PIC aboard an IFR flight or one below VFR weather minimums.
For a pilot receiving instruction to meet the aeronautical experience requirements for an instrument rating (61.65), the flight instructor is considered PIC for all dual training flights conducted under IFR or weather below VFR minimums (1.1).  Therefor for all dual IFR training flights, the instructor must be instrument current to serve as PIC
Now an certified instrument instructor may administer training to meet the aeronautical experience requirements for an instrument rating.  But this not need be done in IFR.  An instructor can provide this training in a sim, FTD, or on a dual instruction flight conducted under VFR.  In these circumstances, the CFII need not be instrument current to administer the instruction and the student can log that time toward an instrument rating.
So flor local VFR training flight with the student under the hood, this is fine.  But if the flight is say filed as IFR, then the CFII must be instrument current to conduct the training.


text:
Why is the CG envelope wider when the aircraft is heavy?
I mean, the same aircraft, but empty or on MTOW. According to MAC, those limits are the same, but the indexes are different. So if I understand that correctly, the CG can be more forward when the aircraft is heavy.

E.g., this Boeing 747 (and all 747s I have seen had an envelope like this), page 20, Report on the serious incident at Oslo airport Gardermoen on 21 September 2004 involving flight KAL520 Boeing 747-400F registered HL7467 operated by Korean Air.

Summary of flight KAL520

So if I understand that correctly the CG can be more forward when the aircarft is heavy.

Not really, although I guess you could say the index can move "forward" because of the way the form is drawn, but the index is not the CG. Indices are a composite number, namely the moment divided by a reduction factor.

The use of index numbers and a reduction factor greatly simplifies
weight and balance calculations, especially for large aircraft. The
index is a moment divided by a reduction factor and may be found by
this formula:
Index = (Weight x Arm) / Reduction factor
(from http://avstop.com/ac/weightbalance/ch4.html)

While indices make manual calculations easier than using %MAC and weight (the way computerized systems typically do it), they do tend to obscure things in my opinion.
If you want to see a 747's weight and balance envelopes using %MAC and weight, go to 747.terryliittschwager.com and select any 747. The top one on the aircraft list will do, N402YY. When the aircraft comes up, scroll down to OPERATING ENVELOPES.
You can position your pointer over the vertices to see their values. Note that the forward limit for takeoff at 580000 lbs is 11.0 %MAC, staying at that limit up to 778000. Getting heavier from there moves the forward limit aft, not forward, and additional weight from there really sends it aft.
The forward limit for the zero fuel and landing envelopes stays constant throughout the weights of their range.

After I read the question, I thought 'unfortunately Terry doesn't contribute here anymore, he would love to answer this one'. But to my pleasant surprise, he did! @Terry, good to see you around here again! I missed your contributions. I hope you are doing well, captain.


text:
What does "transition of glideslope intercept waypoint" mean in the 737 FCOM?
In the Boeing 737NG FCOM, I've read this statement:

VNAV mode is terminated by any one of the following:

selecting another pitch mode
glideslope capture
reaching end of LNAV route
transition of glideslope intercept waypoint if G/S is armed
crosstrack deviation exceeds twice the RNP value during PTH descent for
an active leg with a database vertical angle and LNAV not engaged

In the event of glideslope intercept waypoint transition, VNAV can be re-engaged.

What does "transition of glideslope intercept waypoint if G/S is armed" mean here?

Some context would help, where did you read this?

...and which mark (dash no.) of B737 is it?

I ve read this in the FCOM 737 NG.

@ArcilTralleis I added a longer quote from the 737 FCOM. I think this is what you mean to ask about. If not, please edit again.

Means if glideslope mode is armed in the autopilot on an approach, VNAV mode will terminate and the aircraft will switch to glideslope following for altitude control when the aircraft intercepts the glideslope.

Thank you @Bianfable

As a generic (non-737 specific) answer, it means that when the Flight Director is armed to capture an ILS glideslope, the VNAV flight director mode, being a vertical path based on baro altitude, is cancelled once the aircraft passes through a waypoint that the RNAV system calculates to be the geographical intercept point of the ILS glideslope beam (the intercept waypoint) because the Flight Director is expected to capture and track the ILS glideslope and RNAV/VNAV guidance is no longer required.

I edited for clarification to mention that the "intercept waypoint" is effectively an RNAV calculation of where the glideslope intercept should occur, and at that point the RNAV/VNAV mode is cancelled in the expectation that the FD will now track the radio beam.

More or less in consonance with @John K, here, step by step, is what happens on the later jets:
This is describing the VNAV mode behavior when crossing the "FI" ie the FAF, Final Approach Fix, waypoint, ie the GS intercept point.
The scenario would be that an ILS approach is selected via DEP/ARR page (i.e. from database), and there is a VNAV PATH from the FAF descending to and terminating at ~50ft above the LDG threshold.
If you're shooting an ILS, you're tracking the LOCaliser and the vertical mode is VNAV ALT or VNAV PTH and you're approaching the FAF (depicted as FI).
(Case 1) LOC has been captured GS is armed, the VNAV will disconnect and GS will be captured and become the active mode.
If GS is not armed,
(Case 2a) If the altitude window on the MCP is set to MDA, the airplane will continue on VNAV PTH and commence the descent from the FAF to the MDA.
(Case 2b) If the altitude is set to the FAF altitude or higher in the MCP window, the mode after crossing the FAF will be VNAV ALT.
Thus, in either case of altitude setting, if GS is not armed the VNAV will not disconnect crossing the FI (FI = FAF = GS intercept point)

Holy crap I never knew consonance was a word lol.


text:
If Navier-Stokes equations are unsolvable how does CFD software calculate simulation?
Navier-Stokes equations are one of the problems of the millennium. How, then, are CFD programs doing simulation, calculating forces, etc if these equations are unsolvable?

That's a complete misunderstanding of the challenge. The challenge has nothing to do with solving it at all.

CFD provides a useful approximation, not an exact solution.

@EricS If its is approximation that mean we must neglect some parts inside equation?

Seems like a better fit for Mathematics.

The challenge is about proving the well poseness in 3D, not solving the system.

Prior to my edit, this question was unclear and difficult to understand. I hope my edit made it a bit clearer for some people.

This site has a CFD tag, voting to keep open.

The existence of a tag does not imply a question purely about that tag's subject to be on-topic. Case in point: there is also an aerodynamics tag, but asking about a hydrofoil or F1 wing would be off-topic, because as with this one, the question is not about aviation. In particular, this question is about the general practical solution methods of a physics problem.

@Nij The question asks how the Navier-Stokes can be used for aviation - we have a FlightSimulation tag as well.

The question does nothing of the sort. It asks how CFD software is able to solve the NS equations in simulation. This is a generic physics and/or computational science question. Aviation is not mentioned anywhere, and the only reason you even think it's about aviation is because it's on the aviation site.

The equations solved for the most of the CFD software are the Navier-Stokes equations (let's stay in the general case of compressible ones). The Problem of Navier Stokes equations solution existence means that (only in case of the 3D problem) the solution of Navier-Stokes equations is not proven to "exist and be unique" alias the Lax-Millgram lemma is not verified.
Said so the equation is still solvable. In particular in 2D and 1D this problem does not poses because the lemma is verified.
The most of the CFD software still solve the equations numerically. Even if the well posedness is not verified, it is still possible to solve the equations. Not proving the well posedness it means only that:

"in 3D, solving the Navier-Stokes system, a regular solution is not guaranteed that exist and it is not guaranteed to be unique starting from an initial state and a set of boundary conditions"

I have been fast here, for details have a look at this book for example, in the first chapter there are also basics about the mathematical spaces basis and variational formulation behind Lax-Millgram theorem.

The Navier Stokes cannot be solved analytically, they can however be computed numerically. Which is the technology behind flight simulation, using a determined time interval to compute all dynamic (differential) equations, then use the result as input into the next time interval equation. Real-time digital computation.
The technology is quite mature, as demonstrated by the Newton-Raphson method which dates back a couple of centuries. The Navier-Stokes equations form a matrix of multi-dimensional differential equations, and need to compute the effects of non-deterministic turbulence effects, so they require a lot of computation power with fast iteration loops. Less and less of a problem with increasing computer capacity.


text:
How do missiles navigate and determine their orientation without GPS?
When a missile is engaged in a GPS free tracking loop how is its internal orientation estimated with respect to ground?
I'm assuming this orientation is needed because the force of gravity will be impacting the missiles flight path and this needs to be compensated for, am I wrong? Do they all use IMU? The IMU I have looked at all have bad performance and the cost of extreme precision IMU is greater than the smaller missiles so that can't be the solution.

What kind of missiles are you referring to? Weapons, scientific or hobbyists? If the latter two, please specify some type/types. Among weapons cost is definitely not an issue...

I'm specifically referring to missiles with self guidance systems for target tracking, lets say simple heat seekers like the stinger. I don't think every stringer has a 100k IMU.

highly likely this is classified or under NDA (what I know is, so no answer from me) 2. this is probably off-topic https://aviation.meta.stackexchange.com/q/4292/1467

Basic missile guidance methodology is not classified, as it is simple vector calculus :)

Simple, the missile knows where it is... ;-)

a question for you, asker:  what do you think GPS does?  Orientation directly from GPS is uncommon, but I know it's been done in multi-antenna systems.  Velocity directly from GPS is a bit of a hack (you can derive it directly from Doppler shift).  Really, it's meant for position.

Subverting how to read a marine radar for collision avoidance, about the simplest approach I can think of is to just steer to maintain a constant target bearing, providing the missile is faster then the target they will come together eventually. No need to worry about where the ground is or gravity or any of that stuff. It is not necessarily optimal,  but is cheap, and you don't even need range to target, just bearing.

Before asking "how", ask "if" or "whether".  Given high-speed aerodynamics, rocket propulsion, possible rotation of the missile, the multi-G accelerations of e.g. fighter aircraft trying to avoid the missile, gravity may be one of the lesser and least troublesome forces acting on it.

Are you talking about homing missiles that fly to and attack a specific target like a plane, or cruise missiles that fly to a specific geographic location? The answers are very different for the two, and explains why you have two contradictory answers.

Piggyback on what @ErinAnne said, I would question whether you could even get reasonably good GPS data in a missile given how fast it travels.

@Michael you can get GPS updates at up to 50 Hz, even at Mach 2.5 that's an update every 15 metres. It's even been used in guidable artillery shells https://en.wikipedia.org/wiki/M982_Excalibur

Modern missiles pretty much all determine their orientation via some sort of IMU. Note that you do not need super-expensive RLG-IMU, but you might get away with cheaper MEMS-based IMUs (*1). However (and I cannot stress this enough), it all depends on your specification:

If you know your attitude from your IMU, you can better control your missile as you now are able use feedback-control (*2). Therefore your control-loops can minimize some error. It is also able to compensate for gravity (as you observed) or can actually follow the reference-value of the guidance loop.
You don't even necessarily need a velocity sensor (such as a GPS-unit or a pitot-tube), because you can at least roughly determine your velocity over the accelerometers, or via the known velocity of your missile at the end of the burn or via velocity dependent system dynamics. Kalman Filters are often used in determining the exact system states.

But again, it depends on your specifications. With very tight specifications, you generally need to achieve very high performance in your control loops, which is only possible if you have very good (e.g. expensive) sensor available. If you need to hit the third screw from the left of your target, then you need very precise and expensive sensors. If your warhead is powerful enough to obliterate the target in a 2km radius, you can figuratively just close your eyes and aim in the general direction.
The take-home message is (especially for closed loop control of any flying vehicle) is: Performance and robustness of a control loop are interchangable. The more performance you demand of a control loop, the less robust against sensor noise, external disturbances, system dynamic uncertainties etc. it will be. There are plenty of ways to overcome limitations of missing sensors etc. in order to do something cheaper, however it is up to the designer to check if the product is still be able to perform its task as intended.
Foonotes:
(*1): Expensive and cheap in the military context are a bit different. A cheap MEMS IMU might still cost several thousands of USD.
(*2): Of course you do not need an IMU to close a control loop. Early missile designs directly coupled the angle-to-target (as determined by the seeker) with corresponding fin-deflection. However the addition of an IMU and the corresponding data streams offers more data for possible control loops.

As per comments, this question is referring to guided weapons such as Stinger (IR guidance).
Guided missiles that acquire their target via signal return, such as infrared, radar or laser designation (Homing Guidance, see section 16.4.2) have absolutely no need to "know" their orientation in space. A target lock is established pre or post launch and then maintained by missile sensors, and the sensor signal is then used to calculate necessary maneuvers to steer towards the target.
Any information regarding where in space and in what alignment in reference to earth the missile actually is, is useless: only the position with regards to the target is of importance, as reaching the target is a matter of actions within the frame of reference of the missile, not the earth: the target exist in certain three dimensional(* point in space in relation to the missile sensor. The guidance system updates this "situational image" at certain intervals (several times a second) and the difference between images is used to calculate the rate of change and then the necessary steering inputs.
Adding sensors and algorithms relating to spatial situation with regard to earth's frame of reference add unnecessary complexity (and thus extra fail modes) to this kind of weapons. Within the maneuverability envelope of these missiles the "direction" of gravity is not of crucial importance.
*)To be precise, whether 3-, or just 2-dimensional situation image is actually necessary is an interesting question, as the missiles of this sort are not "throttle-able", so they speed on at full power until target is destroyed or fuel is depleted. Actual or relative speed are therefore of no importance. However, some missiles do not need to impact the target to detonate, so they must have some way to determine the sufficient proximity to the target to arm and explode.

The issue is normally for control you need to know your orientation to predict system response because gravity has a huge influence on flight. It's possible some type of simple PID loop with respect to target center would be good enough for these systems even if some steady error exists but I have never seen the internal operation.

But basically every paper I have read on optimal control in this area assumes knowing full state(even more than orientation). For ground controlled rockets all this makes sense but if your missile is only guided by its internal sensor is much harder, this my question.

I will expound on this in the answer, pls standby.

The fuse is usually completely separate from the guidance system. It just detects an object in proximity at a certain threshold range, not its full 3D position.

@Jpe61 - "some way to determine the sufficient proximity to the target to arm and explode." Yes. That is called, wait for it...a "Proximity fuse". In the case of the AIM-9, it senses when it might be going "past" the target, and explodes. Hopefully punching many holes in it.

Yes, I am familiar with the concept of proximity fuse, but what exactly is the magic by which the said proximity fuse determines the proximity of the object @WPNSGuy

Proximity fuzes go back to WWII; the operation of those early units has long been declassified.  Wikipedia has a good article -- https://en.wikipedia.org/wiki/Proximity_fuze

@FourierFlux: In real missiles you face the tradeoff between more sensors and hitting your performance specifications. For example some short-range missiles do not need to know their exact velocity in order to achieve meaningfull good control, however then the control-system has to be robust enough to steer the rocket over broad enough velocity range. The same goes for attitude control: Sure a Laser-IMU is beneficial, but on a Stinger-type rocket, it might just not be absolutely needed when considering the specifications.

@FourierFlux it doesn't take GPS to know which way is down.  A 3-axis accelerometer will tell you that from the acceleration vector and how it differs from the thrust axis (even if PID isn't enough, which it might well be)

@Jpe61 - Early AIM-9 has an IR sensor for proximity. Later models (AIM-L and later) have a laser. The AIM-120 uses a pulse Doppler prox fuse.

@Therac : however, knowing the relative speed might be useful even for a proximity fuse. For example, in case of aircraft, it matters a lot whether the missile comes from the front or from the back. If it comes from the front and only arms after missing, all the shrapnel will fall far too far behind the target, as the relative speed is too high. But if it comes from behind, then overtaking and exploding can cause damage. What I mean, is that it might be of an advantage to detonate sooner if the relative speed is very high.

@vsz It would be useful. But practical fuses usually work on a simple principle: they arm after some seconds, then illuminate a sector in front of the missile, and if they detect a reflection, within their range, the fuse detonates instantly. The fuse won't arm at all if the missile misses.

@FourierFlux, A simple PID feedback loop is way more than enough. It does not matter whether the target is moving in the sights because the missile is falling with gravity, getting blown aside by wind or the target is moving. Just steer until the target stays still. You only need navigation system for long range.

@FourierFlux As I understand it, the thrust/acceleration on AA missiles is so great and the period of the feedback loop is so short, that gravity doesn't need to be taken into account.  AFAIK, there is no global/optimal path being plotted out, it's just doing adjustments very quickly with a lot of acceleration.

To expand on the answer given by @Jpe61, homing missiles use a technique called 'Proportional Navigation'. It is a surprisingly simple algorithm in which the missile attempts to keep the target on a constant bearing. As long as the missile is reducing the distance to the target this guarantees a hit.
This technique can be implemented using a PID controller where the error signal is the deviation from a constant bearing (detected on a photocell in the case of an IR seeker). The PID output then drives the control fin motors.

Exactly. It does. not even matter which way is up as losing altitude would cause the missile to drop below target (hence the target becomes above the missile) and thus automatically corrects the missile's attitude by steering onto target. Complicated IMUs are used more on cruise missiles and ICBMs that fly long ranges.

Active Skyflash quoting the relevant part where it describes how the missile tracks the target:
http://www.ausairpower.net/skyflash-slammer.html

The Active Skyflash seeker feeds the missile's Integrated Power and
Control Unit (ICPU) with serial signals proportional to target
line-of-sight difference from the missile's boresight in yaw and
pitch, and with a signal proportional to target range. The missile is
steered by cruciform wings, a pair each generating yaw and pitch
inputs, with one pair differentially controlled to provide roll
stabilisation. The wings are actuated by solenoid controlled
hydraulics, the solenoids driven by DC amplifiers fed from digital to
analogue converters (D/A).

Basically, the missile boresight, orientation, and where the seeker head is telling it the target is.


text:
What are these "winglets" on the roof of the 737?
I circled the parts on the fuselage in red.

related: What are the names of the antennas which I have marked in this picture of a Boeing 737?. I though there was already questions about those specific antenna on the B737 here but it seems other questions were about other antenna.

they're for when you're going sideways really, really fast!

In general, those are called blade antennas. They consist of a monopole antenna (a single rod sticking out of the fuselage) with an aerodynamic fairing around it.

It looks like a VHF and ELT antenna.

References:

Boeing 737NG Radio Equipment

Communications


text:
How should I read these abbreviations on the Airbus 320 MCDU?
Often I have seen some abbreviations on the Airbus MCDU such as CI, CF, etc. They are explained in this question: What do the different types of approach abbreviations used on the A320 MCDU exactly mean?
How will I call them when forming my approach briefing? Is there any manual that trains pilots on these abbreviations? I need a quick guide to understand how to interpret these?

I just saw that your "answer" to that other question was deleted. I rephrased your question a bit to avoid it being closed as a duplicate. As far as I understood you want to know how to call them when doing the briefing. If you need anything else, feel free to edit again.

These are RNAV procedures as defined in ARINC 424 used for database coding. They define paths which an aircraft must follow during RNAV departures and approaches. Every standard departure and approach can be divided into distinct sections. Each possible path starts at a point and ends at a termination point. The file format is standardized so that each and every FMS system can read the same file format. You can get an overview at this link.
This document requires pilots to be trained in and familiar with the paths and terminators used in RNAV departure and arrival procedures.

Understanding this terminology gives the pilot a vocabulary and a framework to better understand how an RNAV computer navigates.

RNAV departure and arrival procedures are constructed using legs or segments defined by a path and a terminator.

The path is how you get the, i.e. heading or course
The terminator is the event that causes the start of the next leg, or the end of the procedure.

There are 23 path terminators combinations defined in ARINC 424

13 are used for RNV departure and approach procedures
Each procedure has a two-letter code.

Example:
RNAV procedures start at an Initial Fix (IF) which can be a fly-by or fly-over waypoint, followed by:
Track to a Fix (TF)

The primary straight route segment for RNAV
The segment starts at either an Initial Fix (IF), or the termination of a previous segment.

Direct to a Fix (DF)

Defines a route segment from an unspecified aircraft present position to a specified fix/waypoint.

Course to an Altitude (CA)

Defines an outbound route segment that terminates at an altitude, not at a specific location.

Heading to an Altitude (VA)

Defines an outbound route segment that terminates at an altitude, not at a specific location
Similar to Course to Altitude (CA), but fly an uncorrected heading without regard to wind or ground track.

Course to  a Fix (CF)

Defines a wind-corrected course to a specific fix
Frequently used as the final segment of an approach

Course from a Fix to an Altitude (FA)

Segment begins at a defined fix/waypoint
Requires a wind-corrected heading to maintain course
Terminates when the aircraft reaches the assigned altitude, not a specific location
Common in missed approach procedures.

Others:

Course from a Fix to a Manual Termination (FM)
Heading to a Manual Termination (VM)
Heading to an Intercept (VI)
Constant Radius arc to a Fix (RF)

Every RNAV departure and approach is made up of a combination of the these paths and terminators.
King Schools has an online course for P-RNAV.


text:
What are "approved weather reporting services" and do they apply to part 91?
When I look up Torrance Zamperini (KTOA) alternate minimums, it states, "NA when control tower closed, except for operators with approved weather reporting services."
My main questions are:

Can Part 91 pilots file this airport as an alternate when the control tower is closed?
Do the "operators" restrictions apply to Part 91 pilots?
What is an "approved weather reporting service"?

While we are on the topic, what exactly does the word "appropriate" refer to in the text below? FAR 91.169(c) seems to indicate that almost any source of weather information is acceptable (emphasis mine):

IFR alternate airport weather minima. Unless otherwise authorized by the Administrator, no person may include an alternate airport in an
  IFR flight plan unless appropriate weather reports or weather
  forecasts, or a combination of them, indicated that, at the estimated
  time of arrival at the alternate airport, the ceiling and visibility
  at the airport will be at or above the following weather minima:

welcome to aviation.se. I am afraid that these are quite a lot of questions, it could be better if you could split them in different posts, because as much as they might be related, the answers might be not.

Just a guess, but the only ones who would have operational specifications with approved weather reporting services would be scheduled airlines or Part 135 operators. If the tower is closed, they would presumably have trained personnel to report the weather.

I answered your main question, but like JScarry said, the second question about 91.169 should be broken out into its own distinct question.

First, within the context of the question, the term "operator" in the Alternate Mins section refers to a person or company that has an operating certificate.  Not just Joe the Pilot who is "operating" an aircraft. So, a "Part 91 pilot" (taken from the context to mean: "pilot flying for pleasure or personal business") cannot file this airport as an alternate when the tower is closed.
Second, the term "approved weather source":  In the FARs, various Parts apply to various operators (121, 125, 135). They each have similar verbiage about approved weather reporting services.  For example, Part 121.101 (for domestic and flag operations) says the following (paraphrased):

No certificate holder may use any weather report to control flight
  unless it was prepared by the U.S. National Weather Service or a
  source approved by the U.S. National Weather Service. Each certificate
  holder shall use an approved system for obtaining forecasts and
  reports on each route to be flown and at each airport to be used.

You can see this related question: What sources of weather are approved by the U.S. National Weather Service? for more information.
BUT... the important point from that FAR Part 121 quote is the second sentence. ALL operators must have Operational Specification (OpSpecs) approved by the FAA before they can operate. One of the items within the OpSpecs will specifically address how and from where these weather reports and forecasts will be obtained.
So, this is the bottom line answer to the question: only "operators" can use this airport as a filed alternate when the tower is closed, since that operator will have their own "weather source" that is approved by the FAA and listed in that operator's OpSpecs.

Theory as to why this is so: instead of having automatic weather (ASOS/AWOS), TOA's ATIS and weather reports are made up by a weather reporter in the tower -- without that weather reporter in the tower, there's nobody there to tell folks what the conditions are, and having to do a "look-see" basis for the approach to your alternate is something the FAA doesn't want you doing, so...you can't declare it as your IFR alternate.  No great loss though, because it's still usable for an actual divert, and there are plenty of other choices for a FP alternate in the area (KLGB or KONT would be mine)

I think you may have referred to this, but some operators employ their own meteorologists and would—I presume—have approved weather sources to include their own in-house sources.

Disclaimer: I did not reference the plates.
Operator would include a Part 91 flight.  Approved Wx service is normally ATC, FSS, NWS or a trained observer (which I understand to include pilots).
As for what appropriate means...
I like to interpret things colored by asking myself, "What would the accident review board say?"
In light of that I would consider appropriate to mean that there are METARs and nearby TAFs.  While it appears to be general practice to use a nearby airport with reporting services, it is not clear that is a good practice.  Especially during frontal passage Wx at two nearby airports can be radically different.
So in conclusion, rely on METARs, TAFs, perhaps even PIREPs, but not the Channel 5 news.

Just for clarification,  "operator" does not refer to the pilot, nor is it applicable to Part 91 flights. It only refers to a company with an operating certificate. Also,  "approved wx service" means a plan written by the operator, and signed off on by the FAA.

For part 91, the operator may be a pilot, or as an example, the FAA considers it to be a corporate flight department.

The context of this question is about what is printed in the US Terminal Procedures Publication in reference to Alternate Minimums (Section M).  Within that context, an "operator" is only an entity that has been issued an "operating" certificate under the guidelines of Part 119.  This is not applicable to anyone who may be "operating" under Part 91, including any commercial activities authorized under Part 91.